pH-induced rheological changes for semi-dilute solutions of wheat gliadins

Rheological behaviors of wheat gliadins in 50% (v/v) propanol/water solutions with a concentration of 13 wt% at various pHs were investigated by means of steady and dynamic experiments. Gliadin solutions behave as weak non-Newton liquids with a slight shear thinning. Both zero-rate viscosity and mechanical relaxation time decrease with increasing pH of the solution, which is ascribed to the pH-induced enhancement of intermolecular association. A hybrid model proposed by Ferry et al. [Warren, Schrag, & Ferry, 1973. Infinite-dilute viscoelastic properties of poly-γ-benzyl-l-glutamate in helicogenic solvents. Biopolymer, 12, 1905–1915.] is applicable to account for the dynamic data, suggesting that gliadin macromolecules are partially flexible and are highly elongated due to electrostatic interaction. The experimental results showed that the viscosity and the characteristic relaxation times were related to pH of the gliadin solutions.